1. Field of the Invention
This invention relates to a process for producing a copper-based shape-memory alloy, and more particularly to a process for producing such a memory alloy by powder metallurgy.
2. Description of the Prior Art
Shape-memory alloys of the high strength .beta.-brass type have been hitherto produced chiefly by melt metallurgical processes. Powder metallurgical methods of producing these alloys have also been developed and have been disclosed by, for example, M. Follom and E. Aernoudt, "Powder-metallurgically processed shape-memory alloys", 5th European Symposium on Powder Metallurgy, Stockholm, 1978, pages 275-281. These methods, which employ for the most part fine or very fine powders, are well known in powder metallurgy. On the other hand, some powder metallurgical production methods are also known which use relatively coarse-grained powder as the raw material. These methods are primarily used for the powder metallurgy of titanium alloys and nickel superalloys (e.g., G. H. Gessinger, Brown Boveri Research Center, "Titanium powder metallurgy and composites", International Titanium Conference, Kyoto, May 1980; G. H. Gessinger and M. J. Bomford, "Powder metallurgy of superalloys", International Metallurgical Reviews, 1974, Volume 19, pages 51-76).
If the customary powder metallurgical methods, i.e., mixing, pressing and sintering (possibly with repeated alternate pressing and sintering) are used to produce articles from coarse powders of copper alloys, the densest structures which can be obtained are porous structures resembling filters, which have long been commercially available for special purposes.
Therefore, a need has continued to exist for a method for producing compact, dense copper-alloy articles.